Dynamic direct-radiator loudspeakers of the moving coil type are not capable of operation over a wide frequency range without comparatively severe phase shift and interference effects caused by cone breakup and translation losses. Full range electrostatic loudspeakers, on the other hand, are capable of operation without breakup and translation losses, but suffer from serious problems with respect to directivity because of the large size required for effective bass reproduction. Also, speakers of that type require high operating voltages.
The foregoing problems are minimized by the use of the loudspeaker of the invention. According to one aspect of the invention, a loudspeaker having a balanced (push-pull) electromagnetic drive is provided which is optimized with respect to linearity and efficiency by the configuration of the magnets and conductors. As a result of the configuration, the conductors are subjected to a very uniform magnetic field. The uniformity of the magnetic field is of particular consequence in low or mid frequency portions of the loudspeaker, because the excursions of the diaphragm at high power are greater in these regions. This is especially true in long-throw speakers, wherein peak to peak excursion of the diaphragm may be 0.2 inches or greater.
According to another aspect of the invention, the loudspeaker includes low and high frequency units which are integrated in a single coaxial planar assembly, with the high frequency unit centered between the split halves of the low frequency unit. Sounds produced by the coaxial plane array of this type appear to originate in the center of the array. This configuration results in an excellent transient response. The loudspeaker may be an integrated low and high frequency assembly which serves as a full range loudspeaker. When used in this way, the speaker will usually be mounted on a baffle. Alternatively, the invention may take the form of an integrated mid-frequency, high-frequency assembly which is combined with a low frequency unit. The latter may be either a long-throw induction speaker of the type described herein or a matched moving-coil speaker.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of the preferred embodiments thereof and to the accompanying drawings.